Once in a while i see the following question

Using the Visibile property of the DataGridViewColumn makes this a no-brainer. Let’s take the Databound DataGridView and implement functionality to hide/unhide the quarterly results. All you have to do is add a DataGridViewButtonColumn and handle the DataGridView CellClick event as following

private void dataGridView1_CellClick(object sender, DataGridViewCellEventArgs e)
{
	if (e.ColumnIndex == this.ColumnButton.Index)
	{
		bool visible = !this.ColumnQ1.Visible;
		this.ColumnQ1.Visible = visible;
		this.ColumnQ2.Visible = visible;
		this.ColumnQ3.Visible = visible;
		this.ColumnQ4.Visible = visible;
		this.ColumnButton.HeaderText = visible ? "-" : "+";
	}
}

This is how it looks like

Feel free to download the updated source code for DataGridViewDataSource.zip.